This project is concerned with the development of techniques for the analysis of drug effects on proliferative cell cycle progression and for their application to the characterization of cancer chemotherapeutic drugs and the identification of agents with potential therapeutic activity. The major methods employed in this project are (a) mammalian cell culture techniques applied to the growth of L1210 leukemia cells in suspension culture, (b) flow microfluorometric determinatin of cell DNA content of fluorescent stained cells in a Cytofluorograf (Biophysics Systems, Inc.) and (c) processing, analyzing, and plotting cell DNA content frequency distributions by computer.